Studying the Effect of Climate Change on Drought Conditions and Climate Regions of Iran Using Aridity Index

One of the consequences of climate change is the occurrence of extreme events such as drought, which is important to identify, monitor, evaluate, and inform about the occurrence conditions. In this study, the effects of climate change on the drought situation in the near future (2021-2040), mid-term (2041-2060), and long-term (2061-2080) have been discussed using the Aridity Index estimated by the Copernicus Climate Change Database with the use of GFDL-ESM2M climate model output under RCP4.5 and RCP8.5 scenarios.

In the current research, climate data simulated by the Copernicus database is used to calculate the Aridity Index of different parts in various time horizons. Mann-Kendall's test is applied to investigate the changes of drought indices in different time horizons. Also, the aridity index is used to determine the climatic condition of different parts of Iran in several time periods and its changes are analyzed and investigated.

The results illustrate that in the near future and based on the RCP4.5 scenario, the average annual dryness index has an increasing trend in most parts of the country, and these climate changes lead to a change in the climate of some parts of the north of the country from humid to semi-arid and semi-humid, and parts of the center and the southeast become dry to semi-arid. According to the RCP8.5 scenario, there is a downward trend in parts of the east and the center of the country, and an upward trend in parts of West Azerbaijan, East Azerbaijan, Chaharmahal Bakhtiari, and a part of Kermanshah, and climate change rises the spatial extent of dry climates in the country. Also, in the mid-term and based on the RCP4.5 scenario, a downward trend can be seen in most parts of the country, and climate change will increase the area of dry climate lands in the central and southeastern parts, while according to the RCP8.5 scenario, there is an upward trend in most of the country, and climate change causes a soar in semi-arid and dry climates in parts of the northwest, northeast, and parts of the center and south of the country. Finally, in the long-term and based on the RCP4.5 scenario, the mentioned trends will be almost true and climate change will lead to the expansion of areas with arid and semi-arid climates.

The results obtained in the this research showed that the average drought index in the near future, mid-term and long-term according to the RCP4.5 scenario are 0.5, 2.2 and, 2.3%, respectively and according to the RCP8.5 scenario,  2, 4.2 and, 4.1% have risen compared to the primary period, respectively, and it rises by 1.4 percent compared to the base period, and it is a good indication that the reduction in rainfall and the increase in the temperature of the earth's surface will lead to a soaring in the dryness of different parts of the country. In addition to changing the climate of the region, this issue will have irreparable effects on the condition of water resources, agriculture, environment and urbanization. Therefore, in order to reduce the aforementioned effects, it is recommended that managers and officials consider appropriate measures, correspond to each clime region, to control the amount of water consumption in different parts of the country.